Extraction of metals from heavy petroleum oils utilizing pyridine containing 10-40 percent water



Jan. 26, 1960 L. K. BEACH ET AL 2,922,760

EXTRACTION OF METALS FROM HEAVY PETROLEUM OILS UTILIZING PYRIDINE CONTAINING 10-40% WATER Filed Jan. 28. 1955 2 SheetsSheet 1 I I w l s Bfitxm 6 E w Y .T e m m W m A SEER E T r e Emfiom E on M mzow mh 205 355 w c 358% e a l Fm h e 8w SB m mzoN N T K zotQExm sd h2m 5m m e n mzow NEON m a y V \l\ 295 15 ad B wmfi mww 9 mzmfi g fl 25582? JL T $88. so 53% S T N TH m? w EiEm Jan. 26, 1960 BEAH ErAL 2,922,760

EXTRACTION 0F METALS FROM HEAVY PETROLEUM OILS UTILIZING PYRIDINE CONTAINING 10-40% WATER Filed Jan. 28, 1955 2 Sheets-Sheet 2 ML. WATER ADDED TO MIXTURE 0F I00 ML. OIL AND I00 ML. PYRIDINE FIG-2 James E Shewmaker Leland K. Beach Inventors United States Patent EXTRACTION 0F METALS FROM HEAVY PETRO- LEUM OILS UTILIZING PYRIDINE CONTAINING -40 PERCENT WATER Leland K. Beach, Westfield, and James E. Shewmaker,

Fanwoorl, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware Application January 28, 1955, Serial No. 484,652 6 Claims. (Cl. 208-251) This invention relates to the removal of metal contaminants from petroleum oils, and particularly "as a feed preparation step for subsequent catalytic .cracking of such oil. Thus, in one aspect, the present invention provides a novel process for the upgrading of petroleum feed stocks for catalytic cracking which are normally contaminated with metal compounds detrimental to a catalytic cracking operation. The invention provides a selective extraction process making possible the removal of substantial amounts of metal contaminants from a heavy petroleum oil at high yields of the treated oil. This is made possible by the use of an extraction solvent comprising pyridine or related compounds together with about 10 to 40% of water.

The principal application of this invention relates .to the solvent extraction of petroleum oil fractions boiling in the gas oil boiling range, so as to upgrade these 'frac- 0 tions for use as catalytic cracking feed. The invention entails the use of aqueous pyridine as a selective solvent for metal contaminants normally present in gas oil. The present invention is based on the discovery that aqueous pyridine is uniquely effective for selectively removing metal contaminants from catalytic cracking feed stocks with substantially no loss of hydrocarbon constituents suitable for cracking.

At the present time the process of catalytic cracking is extensively employed for converting high boiling portions of a petroleum crude oil to lighter boiling commercially valuable products including gasoline and "fuel oils. The feed stock to a catalytic cracking unit ordinarily constitutes portions of a petroleum crude oil boiling above the gasoline boiling range or boiling above about 430 F. Such feed stocks may be derived by distillation from virgin crude oils or may be obtained from the products of coking residual oil fractions. Heretofore suchfeed stocks have normally had a final atrnospheric equivalent boiling point of about 800 or 900 F. However, it is economically desirable to include the highest' boiling fraction of a petroleumcrude oil attainable by the vacuum distillation of atmospheric reduced crude. in thiscas'e', 1 the feed to a catalytic cracking unit preferably includes constitutents of the crude oil having an equivalent atmospheric boiling point of up to about 1100" F., or'higher. Consequently, as used herein, the term gas oil'is used to identify this portion of a crude oilboiling in the range of about 430 to 1100 F., or somewhat higher.

Attempts to extend the final boiling .point of gas oil fractions used for catalytic cracking have heretofore been hampered by the presenceof metal contaminants in such in heavy, gas oils are organic compounds of nickel, vana dium and iron, which are particularly objectionable. These organic metallic compounds serve to poison the catalyst used during catalytic cracking so as to materially decrease the selectivity and life of the catalyst. Inclusion of the highest boiling gas oils as catalytic cracking feed stocks has therefore been limited by the economic loss heavy gas oils. Among the metal contaminants present ice " There have been many suggestions aimed at minimizing the metal contamination of heavy gas oils for catalytic cracking feed stocks. It has been known, for example, that residual petroleum oils can be deasphalted in a manner removing a large portion of metal contaminants.

However, complete elimination of metal contaminants ,by,

deasphalting has not been found to be possible. It has also been found that removal of metal contaminants can, be accomplished to some extent by proper fractionation.

of the catalytic cracking feed stocks. Again, however, this technique does not completely solve the problem, in particular, since more volatile metal contaminants cannot be removed by fractionation carried out above about the 1050-1150 F., equivalent atmospheric boiling pointrange.

The present invention is supported by basic research work directed to a determination of the nature of the metal contaminants present in heavy petroleum fractions. This .work has established that the metal contaminants are apparently present in the form of metal porphyrins. It appears that both monomeric and polymeric metal porphyrins occur in oil and that these may vary widely in nature depending upon the nature and length of the radicals attached to the porphyrin nucleus. It has also been established that these metal contaminants can be roughly divided into-.a volatile and non-volatile category in which the volatile metal contaminants can besaid to boil in an equivalentatmospheric boiling .point range of about .1100.rto 1300" R, or possibly higher. Itfollows from this that deasphalting and distillation of heavy petroleum fractions is unsatisfactory for complete elimination of metal contaminants since each of these processes is best adapted for removing only the non-volatile category of metal contaminants. The present invention is of particular significance in providing a technique capable of removing the volatile category of metal contaminants. The process of this invention is therefore of particular utility for the-preparation of catalytic cracking feed stocks in combination with a fractionation or deasphaltingoperation.

The heart of the present invention entails the use of aqueous pyridine as a selective solvent for the removal of volatile metal contaminants from catalytic cracking feed stocks. The possibility of removing metal contaminants by solvent extraction has been appreciated heretofore, and its-has been known that a solvent such as phenol, for example, will extract metal contaminants to however, ,it has been found that extremely selective removal of metaltcontaminants,exclusive of any substantial removal of hydrocarbon. constituents, can be achieved by employing pyridine together with critical amounts of water in the range of about l0 to 40% based on the pyridine. Thus, while pyridine alone ,ismiscible in most 'oils and in any case exhibits poorselectivity for removal of metal contaminants relative vtohydrocarbon constituents, aqueous pyridine exhibits remarkable selectivity for metal contaminants. Thismakes possible use of aqueous pyridine for extraction of metal contaminants providing :treated 'oil fractions of substantially lower content of metal contaminants in yieldswell above 95%.

resulting in the catalytic crackingoperation .due to the presence of these metal contaminants.

The nature and objects of this invention will be fully described in connection withtheaccompanying drawings .andthe following examples ,of 'the invention.

In the drawings: Figure l diagrammatically illustrates a flow plan embullying the principles of this invention, while Figure 2 graphically shows the unique properties of the particular solvent used in this invention.

In order to show the selective solvent properties of the aqueous pyridine used in this invention, reference is made to a number of experiments which were conducted employing aqueous pyridine of variable water content. In these experiments, a Bachaquero crude petroleum oil was subjected to atmospheric and vacuum reduction to obtain a residual oil boiling above 900 F. Using 100 ml. of this residual oil, the residue was extracted with 100 ml. of pyridine and varying amounts of water. Extractions were conducted in a batch manner at ambient temperatures. In order to analytically determine the presence of metal contaminants, the oil feed and oil product were scanned with a recording spectrophotometer in the visible region. It was determined that vanadium contents found by wet ash analyses could be correlated to the optical density at 573 and 536 m,u.. It was furthermore found that the occurrence of other types of metal contaminants such as nickel correlated to the amount 'of vanadium contaminants. Consequently, in these and other experiments, the concentration of metal contaminants is reported as the optical density at the 573 m peak.

In a first series of experiments conducted as described,

a constant oil to pyridine ratio was maintained during extraction 'which was conducted with variable amounts of water. In a second series of experiments, the pyridine to water ratio was kept constant while the ratio of oil to pyridine was varied. The data obtained from these experiments are shown in Table I.

. TABLE I Pyridine-water extractions of 900 F .+Bachaquer residual oil 4 TABLE I-Continue Pyridine-water extractionsfof 900 F .+Bachaquero residual oil-Continued B. Ratio oil-to-pyridine varied; pyridine-water ratio constant at 5 to l Using base line technique for each peak separately.

7 It will be noted from this data that in varying the amount of water present with the pyridine during extraction; the amount of oil which was extracted varied inversely with the amount of water used. Furthermore, it will be observed that the amount of metal contaminants extracted from the oil and contained in the extract phase varied appreciably in accordance with the water content of the extraction system. This is graphically illustrated in Figure 2 of the'drawings which plots the data of Table I. It is apparent from Figure 2 that the water content of pyridine is a critical factor effecting the extraction of metal contaminants. In particular, it will be observed that substantially no extraction of metal contaminants is achieved below a water concentration of about 10% based on the pyridine nor above the water concentration of about based on the pyridine. Furthermore, due to the sharply peaked nature of this phenomenon, an aqueous pyridine having a water content of about 18% is uniquely efiective for removing metallic contaminants in the case of the particular residual oil treated.

The data in the lower portion of Table I indicates that variation of the solvent to oil ratio, maintaining the pyridine to water ratio constant, does not appreciably change e concen ra ion 0 me a con aminan s in e ex rac 'Mln M1 t out!) t-Enrtee th It f H t t th tt 65 g? 3,23; p 37 o ilffii 40 phase over a wide range. In other words, the total volpy n py 573 536 Pi g nine of vanadium extracted appears to be proportional x to the volume of solvent used. Using these basic principles, experiments were then Constant i eti mmmt of T conducted employing an aqueous pyridine solvent. Using v this solvent composition, a Tia Juana crude oil was ex- 100 28 M6 M5 tracted with aqueous pyridine. The extractions were con- 100 24 0.49 ducted in a batch manner at ambient temperatures. The 100 20 0.00 0.44 10s 100 18 M2 0.45 128 pyridine extract phase, obtained by phase separation after 1% i2 8- g-gg l -g extraction, was then subjected to analyses to determine I 100 12 0:10, the transference of metal contaminants from the crude oil r 10 34A to the pyridine extract. The data obtained by these experiments are shown in Table II:

TABLE II Extraction of vanadium compounds from Tia Juana crude with aqueous pyridine Volumes Used, 00. 0.1); Diluted Ext. mg. Metals in an.

. cc. Ext. mg. Oil Run 011 Used Phase in Ext. 11

Oil Pyridine H 0 536 m 573 my V Fe N! A Tia Juana Crude 100 100 20 0.102 0. 235 1: tin s0 25 a 0.135 0. 214 0. 03s 0. 055 0. 04 0.05 0.04:3 0. 005 black 0.56

I Each 100 cc. contains 23.6 mg. V, d= 0.94, V=250 p.p.n1., Ni=16 p.p.rn.. Fe=4.4 p.p.m.

b One ,voi. extract diluted with two vols. pyridine. Optical density determined.

Separation usually incom lete.

p V 1! Contains 1 g. sodium salt. of ethylene diamine tetra acetic acid.

' Slight peak, max. 0.01.

\ By evaporation on hot plate.

paws? n was This data shows that the aqueous pyridine was effective in removingmetal contaminants from crude oil itself.v

In a similar series of experiments, a vacuumreduced residual oil obtained from a Bachaquero crude oil boiling above 900 F. was subjected to pyridine extraction. In. each run 1250 cc. of residual oil was extracted withv 1250 cc. of pyridine and 250 cc. of water. The extraction solvent in other words constituted aqueous pyridine. havi'ng a water content of Twelve successive extracvanadium. 24.1 g. of this distillate fraction was repeatedly extracted with cc.batches of pyridine containing tions were carried out. The results of these runs are shown in Table III:

TABLE III Extractions of 900 F .+residual oil with aqueous pyridine [Total Charge,.1250 cc. oil. Solvent, 1250 cc. pyridine +250 cc. water'for each extraction.]

- OpticalDensity oi Extraction Diluted Unstripped p.p.m.VinExtra-et Extract C $11t f I '011 en 0 Extracts,

Pyridine mg./cc. Un- No. Phase; at 573 m at-536nnt stripped Stripped j cc. 5

1 9 0 (823)} 1172 14.2 i 1.210 2 1, 700 )13? 5:23 11.32 14.4 g 1,270 3'. 1,300 3:22 51% 9.57 11.8 7 1,230 4 1,470 I g; a: 0.45 i 9.9 1,170 1,000 3%? 7.68 8.4 1,094 1,500 3: 7.45 6.8 013 1,500 0.3 h 5.1 810 925 6- 12? 5.32 I 3.9 733 1,850 8 1%,? a: 4.9 v 3.1 033 1,000 g 5.68 3.7 050 1,020 31%; 5 8% 5.07 2.4 v 474 1.415 (4165) @929} 3 4 00050) Initial charge. 545

Complete separation was never obtained. This is volume of phase, not net oil.

b All extracts diluted further with 2 vols. pyridine before optical density measurement. Cumulative values in parentheses.

1 Peaks due to vanadium porphyrin.

Again, it will be seen that the aqueous pyridine was effective in extracting substantial amounts of metal contaminants from the residual oil. The data also brings out the small amounts of oil carried over into the extract phase even though complete separation of the extract 5. cc. of water. The data obtained in, these runsis shown in Table IV. a

TABLE IV Extraction of molecular distillate from 900 F..+- residual oil phase was'not attained. Thus, in run No. 7, for exam- Extraction on Diluted ple, of an extract phase having a volume of 1500 cc., Pyridine Phase the oil content amounted to only 6.3 mg./cc. It will c c: 1 Extract? 3 5 also be observed that in the successive extractions con- 123 35 5 @536 Phase :Raflmate ducted, the vanadium content of the residue was reduced by substantially 30%.. While successive extractions &3 32-8 would be expected to remove somewhat greater amounts 81' 0375 0147 14:0 3 201 3 of vanadium, it is apparent that complete removal of 81: 2 81%; 1 i1? metal contaminants from the crude oil could not be I 3 8 8?; 3 2 2;; obtained by aqueous pyridine extraction. This data indi- I I cates that the aqueous pyridine was efiect'ive in extract- 200. pyridine hase diluted with4cc.oi t measurement p I V V V pynd c for opticaldensity Percent on Charge 1pm the data bums table, it will be seen that the aqueous pyridine was effective in extracting substantially all of the metal contaminants present in the distillate fraction. Considering this data in connection with the data of Table III, it is therefore shown that aqueous pyridine exerts a selective solvent action toward volatile metal contaminants boiling up to about 1300 F. or somewhat higher. Metal contaminants boiling significantly above this range are apparently not efiectively extracted by aqueous pyridine.

The present invention has been described with reference to pyridine itself and is considered of particular utility when employing this specific compound. However, alkyl substituted pyridine may be employed, and particularly the methyl substituted pyridines. This makes possible the use of mixed pyridine type compounds including crude pyridine in the process of this invention. Data obtained for such extraction agents are shown in the following table, employing the techniques described hereinbefore:

TABLE V Extraction of 900 F.+residual oil Optical Density of of Extracts I Oil Content of Extracts Solvents (mg. oil per Pyridine-water 2-Methyl pyridine-water- 3-Methyl pyridine-water. s-Methyl pyridine-water.-. 2,6-Dimethyl pyridinc-water. 2,4-Dimethyl pyridine-water Spectrum on solution of 2 ml. of extract in 4 m1. of pyridine.

San Joaquin, Sweden "and West Texas crude oils and boiled in the upper part of the range of about 700 to- This gas oil was extracted in a countercurrent multistage extractor in runs employing 5 and 20 countercurrent stages of contacting. During these runs a temperature gradient was maintained along the extractor in the manner customarily employed in plant scale extractions. The results of these experiments are shown in the following Table VII.

It will be observed that the aqueous pyridine served to greatly drop the content of nickel contaminants. However, due to the extremely selective nature of the solvent,

treated oil was obtained in yields above 96 weight percent.

In this connection, it was observed by chromatographic analysis that the loss in oil yield relates to reor normal heptane cannot be employed, since such compounds are not soluble in aqueous pyridine and since they exert a selective solvent action toward metal porphyrins which would tend to retain these in the oil raffinate.

Ho e

wev It was found that aromatlc compounds and ,7 line 3, while higher boiling fractions such as gasoline particularly xylene, toluene and benzene actuallyimprove the efliciency of metal removal and therefore can be used for reducing the viscosity of a heavyoil to be treated. Experiments demonstrating the particular utility of xylene, are shown in Table VI.

TABLE VI Oase 1 Water Optical Densities:

Peak at 575 mp- Ext. Phase, Vols 80 Oil in Ext. Phase, mg./cc. Oil Extracted due vacuum distillation operation was subjected to aqueous pyridine extraction.- The gas oil was a bottoms side stream derived from the vacuum distillation of mixed moval of essentially no parafiins or naphthenes but only the extremely aromatic and polar materials which would be of poor cracking quality. Consequently, this data shows the particular utility of aqueous pyridine for upgrading heavy gas oil for catalytic cracking.

While the process of this invention may be embodied in a number of techniques, in refining operations, Fig ure 1 of the drawing illustrates a preferred embodiment of the invention. In this drawing the numeral 1 designates an atmospheric distillation tower, which may be of conventional character. A crude oil may be brought into tower 1 through line 2 wherein it is fractionated into any desired number of difierent boiling streams. Thus, light gases may be removed from the top of zone 1 through and heating oil may be withdrawn through sidestream withdrawals 4 and 5. A reduced crude fraction which may, for example, boil above about 700 F., may be withdrawn as a bottoms product through line 6.

This reduced crude fraction may then be subjected to vacuum distillation in zone 7 with or without fractionation below the exit line 8. In distillation tower 7, a high vacuum is maintained to permit recovery of high boiling distillates without cracking. For example, operation may be adjusted to secure removal through line 8 of 'a heavy gas oil boiling in the range of about 450 to 1300' F. Lighter fractions may be removed through higher points of the tower including the upper withdrawal line 19, while the heaviest fraction may be withdrawn as a bottoms product through line 20. In accordance with .the data describedkherein, the heavy gas oil stream of line 8 will include volatile metal contaminants originally present in the crude oil. Non-volatile metal contaminants will be concentrated in the residual fraction withdrawn from line 20. The heavy gas oil of line 8 is then subjected to solvent extration in tower 9 employing aqueous pyridine introduced through line 10 as an extractive solvent. Contacting may be carried out in a countercurrent or staged extraction tower of the nature illustrated in which aqueous pyridine will drop downwardly through the tower countercurrent to the drawn from the top of the extraction tower through line 11 comprising the treated gas oil having substantially less metal contaminant content than the gas oil of line 8. This treated gas oil is stripped in zone 18 and the pyridine-free oil is then preferably subjected to catalytic cracking in zone 12. The aqueous pyridine taken over in line 24 is condensed and recycled. The catalytic cracking may be carried out in the conventional manner employing conventional catalysts. For example, the catalyst may be of the metal oxide type and preferably will include silica-alumina, silica-magnesia, or silica gel, promoted with metal oxides which are adsorbed thereon. Typical cracking conditions are at temperatures in the range of about 750 to 1050 F., and pressures ranging from atmospheric to somewhat about atmospheric pressure.

The extract phase removed from zone 9 through line 14 will consist of the spent aqueous pyridine together with minor amounts of the gas oil introduced into zone 9. Pyridine may be recovered from this extract phase for recycle to the system by passing the extract phase to a stripping zone 15. Stripper 15 may be operated to drive water and pyridine over-head for removal and recycle through line 16 and to permit removal of the oil extract constituents through line 17.

In the conduct of solvent extraction zone 9, the extraction agent Will constitute pyridine together with about to 40% of water, preferably about 20% of water is employed with the pyridine constituting the extraction agent. Based on the oil to be treated, treats of about 50 to 500 volume percent may be employed, although use of about 1 to 2 times the volume of oil is preferred. It is a particular feature of this invention that the extraction can be carried out at ambient temperatures, although elevated temperatures can be employed particularly in order to decrease the viscosity of the oil aiding in effective phase separation. Again, pressure is not a critical factor in the aqueous pyridine extraction, so that atmospheric pressure or elevated pressures can be employed.

As described and as shown by the data referred to, the aqueous pyridine extraction of this invention is of particular utility to the treatment of heavy gas oils intended for catalytic cracking. In this application, the invention is applied to virgin petroleum distillates or gas oils from coking operations which distillates or gas oils boil above about 450 F., especially those above 1100" F., ranging upwardly to about 1300 F., or even higher. As emphasized, application of this invention to such a distillate fraction is particularly desirable in providing a fraction in which the metal contaminants present are of a volatile nature and are completely extractable by the aqueous pyridine. However, the invention is also of application to the treatment of the crude oil itself or to residual fractions of crude oil. In these cases, it is a particular feature to employ the process of this invention in combination with a deasphalting operation. Thus, as formerly pointed out, deasphalting may be conducted so as to remove non-volatile metal contaminants so that removal of volatile contaminants by the aqueous pyridine extration can be used in combination with deasphalting to substantially diminish or eliminate all metal contaminants.

What is claimed is:

1. A process for removing metal contaminants from high boiling fractions derived from a petroleum crude oil, including hydrocarbon constituents boiling above about 900 R, which comprises contacting said fraction with an extraction agent consisting of a compound selected from the group comprising pyridine and alkyl substituted pyridines together with about 10 to 40 parts of water per parts of the pyridine, whereby metal contaminants may be removed.

2. A process for providing high quality high boiling catalytic cracking feed stock in which a reduced crude oil fraction boiling up to about 1300 F. is contacted with an aqueous pyridine having a water content of about 10 to 40 parts per 100 parts of pyridine, and recovering a raflinate product consisting of catalytic cracking feed of substantially reduced metal content.

3. The process defined by claim 1 in which the said contact is carried out in the presence of an aromatic hydrocarbon selected from the class consisting of xylene, benzene, and toluene.

4. The process defined by claim 1 in which the said extraction agent has a water content of about 20 parts per 100'parts of pyridine.

5. The process defined by claim 1 in which about 50 to 500 volume percent of extraction agent is employed per volume of the petroleum fraction.

6. A process for segregating metal contaminants from a petroleum crude oil comprising fractionating said crude oil to obtain a fraction boiling within the range of about 430 to 1300 F., whereby extractable metal contaminants are concentrated in the said fraction and thereafter contacting said fraction with an extraction agent consisting of a compound selected from the group comprising pyridine and alkyl substituted pyridines together with about 10 to 40 parts of water per 100 parts of the pyridine, whereby metal contaminants may be removed.

References Cited in the file of this patent pages -127. brary.)

(Copy in Patent Office Scientific Li- 

1. A PROCESS FOR REMOVING METAL CONTAMINANTS FROM HIGH BOILING FRACTION DERIVED FROM A PETROLEUM CRUDE OIL, INCLUDING HYDROCARBON CONSTITUENTS BOILING ABOVE ABOUT 900* F., WHICH COMPRISES CONTACTING SAID FRACTION WITH AN EXTRACTION AGENT CONSISTING OF A COMPOUND SE LECTED FROM THE GROUP COMPRISING PYRIDINE AND ALKLY SUBSTITUTED PYRIDINES TOGETHER WITH ABOUT 10 TO 40 PARTS 